A Sensitive Fluorimetric Method for the Determination of Nitrite and Nitrate in Seawater by a Novel Red-Region Fluorescence Dye

A novel method for the determination of dissolved inorganic nitrite and nitrate in surface seawater was reported, which is based on the diazotization reaction between nitrite and a novel red-region fluorescent dye, tetra-substituted amino aluminum phthalocyanine (TAAlPc). Nitrate is determined as nitrite after reduction on a cadmium column. Under optimal conditions, the linear range of the calibration curve is 21–840 nM for nitrite. The detection limit is 7 nM for and the relative standard deviation for six replicate measurements of a 350 nM nitrite solution is 3.2%. Since the method employs a red-region fluorescent dye (λex/em = 610 nm/678 nm), the potential fluorescent background resulting from the organic matters in seawater can be eliminated and thus the sensitivity of the method can be enhanced.